hmm, really odd, pin 3 and 13 are indeed marked as "step", but the connections are
not labelled in the chip, so i don't know what they do.
just a few observations:
-you will need motors with a tap in the middle of each coil (i.e: 6 wire step motors,
while many (most?) step motors have only 4 wires.
-the S1 switch is only connected to inputs, so that wire will work as an antenna if
it's in the middle of the switch (i.e: rattle between + and - at a few MHz), tho the
rest of the electronics may take care of this, it's still better to avoid.
A more conventional way is to connect the input via a (10k) resistor to +12V and
then just a single switch to pull it down to 0V. (i.e: switch open: +12V.
switch closed: 0V)
-this circuit cycles through the 4 possible motor stages, but there is no reset, so you
(or the computer that is generating the steps does not know what the initial stage is)
What are you trying to do?
Do you want to drive the step motor from a printer port of a computer?
What kind of step motor do you have ?